Traditionally, there has been known a high pressure pump for pressurizing fuel sucked from a fuel tank by a low pressure pump and for supplying the pressurized fuel to an internal combustion engine. The high pressure pump has a pulsation damper for reducing a pressure pulsation in a fuel chamber communicating with a pressurizing chamber in which the fuel is pressurized. In the pulsation damper, the peripheral edge portions of two diaphragms are welded to each other and gas having a pressure equal to or higher than the atmospheric pressure is trapped inside the two diaphragms. The two diaphragms are displaced according to a pressure change in the fuel chamber to thereby change the volume of the fuel chamber, whereby a pressure pulsation of the fuel is damped.
A pulsation damper described in Japanese Patent No. 423567 is fitted in a fuel chamber in a state where the peripheral edge portions of diaphragms constructing the pulsation damper are sandwiched by an upper support member and a lower support member. In this way, the pulsation damper is inhibited from being displaced in a direction in which the peripheral edge portions of two diaphragms constructing the pulsation damper are separated from each other by a pressure pulsation in the fuel chamber.
However, the pulsation damper described in Japanese Patent No. 423567 is liable to present the following problems (1), (2), and (3). (1) In the upper support member and the lower support member, in order to prevent a stress developed by the displacement of the diaphragm from being applied to the welded portion of joining the peripheral edge portions thereof, end faces abutting on the peripheral edge portions of the diaphragms need to be formed in parallel to the peripheral edge portions For this reason, the working cost of the upper support member and the lower support member is increased. (2) In the upper support member and the lower support member, in order to prevent the stress developed by the displacement of the diaphragm from being applied to the welded portion of the peripheral edge portions thereof, the peripheral edge portions of the diaphragms need to be pressed over the entire circumference by the same load. For this reason, in the upper support member and the lower support member, an area of a conical portion of connecting an end face abutting on an inner wall of the fuel chamber with an end face abutting on the peripheral edge portion of the diaphragm is made large. For this reason, the flow of the fuel in the fuel chamber is prevented by the upper support member and the lower support member. (3) In order to prevent a twisting force from being applied to the diaphragms, the upper support member and the lower support member need to be fitted to the diaphragms in such a way that the center of the upper support member is aligned with the center of the lower support member. For this reason, the working accuracy and the fitting accuracy of the upper support member and the lower support member need to be improved and hence a manufacturing cost is increased. Further, in the case where the upper support member and the lower support member are formed by a press, it is difficult to decrease a manufacturing tolerance in such a way that the center of the upper support member is aligned with the center of the lower support member.